Nowadays apparatuses and devices for generating images and for projecting the same as well as their miniaturization become more and more important in many customer devices and electronic appliances. The problem of such apparatuses and devices—in particular when using light sources which at least to some extent produce or at least involve coherent light—is that in the process of image generation and image projection the produced images contain noise and other inhomogenities which are due to the coherent nature of the involved light. These inhomogenities are in part in particular caused by interference processes at optical faces, surfaces or interfaces. The noise component is usually called speckle and is generated majorly by interference processes, for instance at diffusing faces or interfaces, e.g. at diffusing screens.
These circumstances are also given when using a plurality of different light sources having coherence properties and having different spectral properties, e.g. different colours.